1. Field of the Invention
The present invention relates to a driving apparatus which comprises two movable elements, an exposure apparatus, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2004-254489 describes an exposure apparatus which comprises a stage device having two wafer stages. Such an exposure apparatus can execute alignment measurement for the wafer on one stage while exposing the wafer on the other stage. In an exposure area, the wafer can be exposed by projecting the pattern onto it via a projection optical system. In a measurement area, alignment measurement can be done by measuring the position of the mark on the wafer using a measurement optical system. The two stages can be swapped between the exposure area and the measurement area.
The stage device comprises two movable elements which function as stages, and a stator having a flat portion. Each movable element comprises an almost rectangular parallelepiped top plate, a plurality of permanent magnets provided on the lower side of the top plate (stator side), and a substrate holding unit (substrate chuck) provided on the top plate.
The stator comprises a coil unit. FIGS. 18A and 18B are views showing the arrangement of a coil unit of a stator. The coil unit includes first coil arrays 171, i.e., 171a, 171b, and 171c for driving in the X, ωz, and ωy directions, and second coil arrays 172, i.e., 172a and 172b for driving in the Y, ωz, and ωy directions. The first coil arrays 171 and the second coil arrays 172 are superimposed on each other.
The first coil arrays 171 are formed by juxtaposing, in the X direction, a plurality of coils which have straight portions along the Y direction and produce a thrust in the X direction. The second coil arrays 172 are formed by juxtaposing, in the Y direction, a plurality of coils which have straight portions along the X direction and produce a thrust in the Y direction.
To execute the alignment measurement process and exposure process in parallel, the two stages (movable elements) must be driven independently. As shown in FIG. 18B, the first coil arrays 171 including coils which produce a thrust in the X direction are formed by juxtaposing, in the X direction, a plurality of coils which have straight portions along the Y direction and produce a thrust in the X direction. This makes it possible to independently drive the two stages (movable elements) to execute the measurement process and exposure process in parallel. However, to swap the two stages by respectively driving them in the +Y direction and −Y direction, the two stages must be driven independently even when they align themselves in the Y direction. To meet this demand, the first coil arrays 171 include swap coil arrays 171c1 and 171c2 which are divided in the Y direction. As a result, the first coil arrays 171 include the coil array 171a for the measurement process and swap process, the coil array 171b for the exposure process and swap process, and the coil arrays 171c1 and 171c2 dedicated to the swap process.
As shown in FIG. 18A, the second coil arrays 172 including coils which produce a thrust in the Y direction are divided in the X direction. The divided coil array 172a drives the stage for the measurement process and swap process, while the divided coil array 172b drives the stage for the exposure process and swap process.
In the exposure apparatus disclosed in Japanese Patent Laid-Open No. 2004-254489, the first coil arrays 171 have the coil arrays 171c1 and 171c2 dedicated to the swap process, in addition to the coil arrays 171a and 171b. The coil arrays 171a, 171b, 171c1, and 171c2 are two-dimensionally juxtaposed. This increases the installation area (footprint) of the stage device or exposure apparatus by the areas occupied by the coil arrays 171c1 and 171c2 dedicated to the swap process.